


Expecto Patronum

by FantasticNumberNine



Series: John Watson and the Prisoner of Azkaban [11]
Category: Harry Potter - J. K. Rowling, Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: AU, Crossover, Dementors, Gen, John and Mycroft discuss Doctor who, M/M, Potterlock, not hunting things, saving people, there is no family business
Language: English
Status: Completed
Published: 2017-01-08
Updated: 2017-01-08
Packaged: 2018-09-15 20:57:11
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,885
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9256961
Author URL: https://archiveofourown.org/users/FantasticNumberNine/pseuds/FantasticNumberNine
Summary: John wakes up in the hospital wing, discovering that an innocent man is about to receive a Dementor's kiss, and that one of his best friends has been playing the Doctor all year. Can they save Sirius Black from a fate worse than death?





	

**Author's Note:**

> *disclaimer*
> 
> I do apologize.

John decided, possibly unfairly, that things had only truly started to go bad with the untimely appearance of Snape. 

There were dementors everywhere; Mycroft knew the spell, had demanded John show him everything about the Patronus Charm after each lesson with Professor Lupin.

Professor Lupin had run off into the Forbidden Forest--in his werewolf form, with his werewolf mind, because he'd forgotten his potion.

Dementors. Everywhere. Greg was unconscious. Snape was unconscious—useless, and his own fault, sticking his huge bloody nose in where he was certainly _not_ invited.

Sirius Black! He was innocent! It was Pettigrew, the traitor! Not Sirius—

" _Expecto Patronum!_ "

Mycroft stumbled beside him, his pale face grey and glowing with perspiration, his wand slipping from his trembling hand—he'd practiced in their dormitory, never against the real thing.

"John..." 

They were everywhere. And now John was alone. 

" _Expecto..._ "

Alone.

" _Expecto..._ "

——————————

John shot up with a choked gasp, half tangled in sterile white sheets.

"John!" Mycroft hissed from the bed to John's right, he held a finger to his lips then gestured for John to lie back down, throwing a significant look towards the slightly open door.

Snape and Cornelius Fudge were conversing in low voices just outside the darkened hospital wing. 

"—Watson has always been allowed an extraordinary amount of license by the Headmaster—"

"Ah, well, Snape... John Watson, you know... We've all got a bit of a blind spot where he's concerned."

"And yet—is it good for him to be given so much special treatment? Personally I try to treat him like any other student—"

John scoffed, then muttered, "Yeah, and I'm so grateful."

"Ah, you're awake!" Madame Pomphrey came briskly down the aisle, carrying the biggest block of chocolate John had ever seen to his bedside. 

"How is Gregory?" Mycroft asked, shooting the smallest glare John's way for alerting Madame Pomphrey to their wakefulness and cutting off his ability to listen to the conversation going on just outside.

"He'll live; as for you two, you'll be staying here until—Watson! Where do you think you're going?"

John was grabbing his wand and rolling off the bed.

"I need to see the Headmaster," he said.

"Watson, you needn't worry yourself. They've caught Black, he'll be receiving the Dementor's kiss at any moment—"

"WHAT?"

Mycroft jumped out of his bed too, now, a cold look in his eyes as he took in the Minister and Snape, who had burst into the hospital wing after John's shout.

"What's this? John! You should be in bed—" said Fudge, twitchy and agitated.

"You're gonna let those things Kiss Sirius Black! Are you really that stupid?" John growled, "He's innocent! We saw Pettigrew, he's alive!" 

"Now, now, John, you're confused! Lie back down, we have everything under control—"

"If by under control, you mean you're punishing a man without trial, again, then I fear for the future of Britain's magical community," Mycroft sneered. "At least five witnesses saw Peter Pettigrew alive tonight, and any competent minister would—"

"You see, Minister?" said Snape. "Confunded, both of them—"

"WE'RE NOT CONFUNDED!" John roared.

"Minister! Professor!" Madame Pomphrey cut in angrily. "I must insist that you leave, these boys are my patients, and they should not be distressed!"

"Distressed!" John shouted, outraged. "They're not listening! I—"

Madame Pomphrey stuffed a small block of chocolate into John's mouth and pushed him back onto his bed, just as the door burst open once more and Dumbledore came striding in.

"Professor Dumbledore—" John said around half a mouthful of chocolate.

"Oh, for heaven's sake, Albus! These children—" Mycroft squawked indignantly— "Need rest! I must insist—"

"My apologies Poppy, but I need a word with both mister's Watson and Holmes," Dumbledore said, quite calmly. "I have just been talking to Sirius Black—"

"I suppose he's told you the same fairytale he's planted in Watson's mind?" Spat Snape. "Does my evidence count for nothing? I saw no sign of Peter Pettigrew in the Shrieking Shack or anywhere on the grounds."

"Well, you did spend most of tonight unconscious, Professor," said Mycroft tightly, as he stood beside John's bed. "And unashamedly biased the rest of—"

"Mister Holmes, HOLD YOUR TONGUE!"

"Now, Snape, the young man is disturbed in his mind," Fudge stammered.

John felt Mycroft's hand clench around a fistful of sheets; he covered Mycroft's hand with his own, squeezing slightly.

Dumbledore gazed calmly at his audience, "We will only need a few minutes."

Snape swept out of the infirmary with a dramatic turn of his robes, and minister Fudge followed, sputtering the whole way. Madame Pomphrey pursed her lips in disapproval, but locked the door behind her.

Dumbledore turned his sharp gaze to Mycroft; "What we need, is more _time_."

A faint smile touched Mycroft's lips as his hand fiddled with a fine gold chain around his neck. John frowned, confused.

"I don't understand—"

Dumbledore cut him off, "With luck, you may be able to save _two_ innocent lives tonight."

John looked between Dumbledore and Mycroft, "Is no one going to explain what the hell—sorry, professor—is going on?"

Dumbeldore's eyes twinkled behind his half moon glasses, but he didn't answer John's question; "Three turns should do it, Mister Holmes."

And then he swept out calmly from the infirmary. 

John gaped after him; until Mycroft pulled him out of his bed, throwing a fine gold chain around his neck.

"Ready?"

"Ready for what? Dammit, Mycroft—"

They were no longer in the infirmary, everything blurred, and whatever he had been about to say to Mycroft lost itself in an unintelligible shout and a twist of color. Almost as suddenly as it began, everything stopped and John half fell into Mycroft, who was smirking, but only just. 

Whatever had just occurred—and John would find out—had brought them into the Entrance Hall, a beam of sunlight pouring into the Hall through the open doors.

"What the hell, Mycroft?"

"Hush," Mycroft said softly, pulling them both into the nearest broom cupboard. "We'll hear us."

"What—"

Mycroft cut him off with a short kiss, before murmuring, "We've time-traveled, exactly three hours, backwards. Listen:" Quiet footsteps crossed the hall and out onto the grounds. "That was us. We'll wait another minute before following—it is imperative, John, that our past selves do not see our current selves, do you understand?"

"Time-travel?" John hissed.

"Godric save us," Mycroft squeezed his eyes shut.

"Is this how you've been getting to all your classes? Like Doctor Who?"

Mycroft gaped at him, and John turned, opening the door to their cupboard cautiously. "We're on our way to Hagrid's aren't we? That's quite a bit of time before—oh! We can save Buckbeak!" 

Mycroft shook himself, mentally, before following John out of the cupboard. "You are unexpectedly delightful when you are unpredictable, John."

The back of John's ears and neck blushed bright red, and Mycroft felt his own face flush. 

"I had not intended to say that aloud," Mycroft muttered.

John turned, his face pink but smiling as he grabbed Mycroft's hand, "You can call me delightful whenever you'd like, Mycroft."

At this rate, Mycroft's own blush would never recede, he thought as they snuck quietly down to Hagrid's, hand in hand.

They waited in the trees behind Hagrid's hut until the last possible moment before tugging Buckbeak to his freedom—there had been one nerve-wrenching moment when John would have burst in and grabbed Pettigrew, if Mycroft hadn't pulled him down and sat on his back. 

And then they waited some more. John was itching to do anything, settling unhappily for pacing inside the tree line, glancing out at the whomping willow every row steps. 

"Sit down, John, your pacing is only serving to agitate poor Buckbeak."

John flopped down beside Mycroft, "Time travel is never this boring on Doctor Who."

"They edit out the waiting bits for the sake of time," said Mycroft, shrugging.

John snorted. 

"I didn't think you'd know Doctor Who," Mycroft said, glancing at John sidelong. 

"I'd watch it with Mrs. Figg, when she wasn't showing me off to all her cats. And sometimes, when the Dursley's left me at home by myself," John paused to glare at his hands. "I'm rather good at picking locks."

Deciding it was time to change the subject, Mycroft asked, "John? There's something about tonight that I don't understand."

John glanced up at him, eyes wide.

"I don't know everything, John," Mycroft rolled his eyes.

"I'm going to remember this moment for, ever, I think."

"And you'll make sure to remind me as well, I'm sure, can we move on now?"

John grinned, "Of course. You were saying that you didn't understand something?"

"You are exasperating," Mycroft sighed. "Earlier, for us, the dementors had us surrounded. But when we came to in the hospital wing, none of us had been kissed, not even Sirius Black."

"There was a man, across the lake. He cast a Patronus and it chased the dementors away. It was a stag, and I think, I think..." John sucked in a deep breath. Impossible. It was impossible.

Mycroft squeezed his hand, "John, you know it wasn't—"

"I know. I was delirious, by that point. It could have been anyone," he turned away from Mycroft, hoping to hide the glossy shine of his eyes.

Mycroft cleared his throat, before using his free arm to pull John into an awkward hug, worth his discomfort when John huffed a small laugh. 

"Thanks," John muttered as he pulled away. He wiped at his eyes with one hand, then stood abruptly, pulling Mycroft up after him. "Here we come."

Mycroft peered out at their earlier selves, then paled. "John, we have to move."

"What?" John looked up at Mycroft, the back out at themselves. "There goes Lupin—fuck. Run!"

They ran back to Hagrid's, grateful that it took no coaxing to convince Buckbeak inside with them. Breathing hard, Mycroft squinted at John. John glared softly back, "What now?"

"It's obvious, isn't it, John? Everyone is always saying how much you look like your father, and tonight, earlier, _soon_ , you're going to believe you've seen him, your father, across the lake, casting a Patronus, _your_ Patronus, to save us from the dementors."

John stared at Mycroft for a long moment, before tearing out of Hagrid's hut and to the lake. He could see his silvery attempts across the water, saw the dementors closing in. It hadn't been his father, saving them. It had been him, all along. 

" _EXPECTO PATRONUM_!"

————————————————

As the Hogwarts Express pulled out of the station, Mycroft announced that he had dropped muggle studies, giving up the Time-Turner with it—Greg was still miffed that Mycroft had kept it a secret.

"You'll have to come stay with us this summer, John. I'll fix it up with mum and dad, then I'll call you. I know how to use a fellytone now—"

"It's a _telephone_ , Gregory, maybe you ought to take muggle studies next year."

Greg ignored him.

"It's the Quidditch World Cup this summer! Dad usually gets tickets through work, you have to come with us!"

Cheered up considerably by the prospect, John joined in several games of Exploding Snap, before a tiny owl interrupted their game.

_I, Sirius Black, John Watson's godfather, hereby give him permission to visit Hogsmeade at weekends._

"That'll be good enough for Dumbledore!"


End file.
